Exhaust arrangements for powder spray booth

ABSTRACT

A paint spray booth utilizes an exhaust system extending longitudinally along the path of the articles to be painted having an adjustment mechanism for varying the width of the exhaust inlets extending longitudinally for substantially the entire length of the air exhaust element and a downwardly slanting bottom surface of the exhaust elements for yielding powder overspray of uniform density to a filter media. Adjusting the width of the longitudinally extending exhaust inlet spreads an adjustable pressure drop over the slot opening. Adjusting the velocity of air flow through the exhaust elements substantially avoids powder paint build-up at the exhaust inlet. The slanted configuration of the exhaust elements, in conjunction with the adjustment mechanism, improves uniformity of filter life by providing a substantially even distribution of powder overspray to a filter media. The invention finds particular advantage in powder spray booth applications and is adapted to modularization thereby enabling retrofitting of existing spray booths with apparatus arranged in accordance with the principles of the invention.

This is a continuation-in-part of United States patent application Ser.No. 08/315,126, filed Sep. 28, 1994.

BACKGROUND OF THE INVENTION

This invention generally relates to exhaust systems for paint spraybooths. More particularly, the invention concerns air exhaust elementshaving an adjustment mechanism for varying the width of exhaust inletsextending longitudinally for substantially an entire length of a paintapplication zone in the booth and a downwardly slanting bottom surfaceof a duct of the exhaust element for yielding powder overspray ofuniform density to a filter media.

Designers of conventional paint spray booths have traditionallyattempted to improve paint exhaust efficiency therein. Much of the paintspray, especially in powder spray booths, never reaches the target beingpainted and becomes so called "overspray", which must be removed from anair stream in the booth.

In one type of known arrangement, multiple exhaust boxes are positionedalong the path of the articles to be painted. Paint overspray gravitatesinto the lateral exhaust boxes and is passed through a cartridge filter.In this arrangement, the exhaust boxes positioned generally beneath thepowder spray guns of the paint booth capture a greater percentage of theoverspray than the other exhaust boxes. This configuration results innon-uniform powder overspray concentrations within the exhaust boxes andnon-uniform filter life. Additionally, in booths of this type, quickaccess for filter replacement or maintenance is difficult to achieve. Insome cases, sections of the grated flooring overlying the powderfiltration apparatus must be removed for such access, thereby forcingincreased booth down time.

Another known approach to recover overspray in a powder spray booth istaught in U.S. Pat. No. 5,178,679 to Josefsson, which is herebyincorporated by reference, wherein exhaust elements extendlongitudinally along the path of the articles to be painted. Paintoverspray gravitates through apertures that run the length of theexhaust elements and is conveyed to a recovery system. However, none ofthe art presently known to Applicant suggests using an adjustmentmechanism to vary the width of an inlet opening of an exhaust element ora downwardly slanting bottom surface of an exhaust element to yieldpowder overspray of uniform density to a filter media regardless of themedia's location along a longitudinal axis of the spray booth forimproving uniformity of filter life.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an air exhaust system in apowder spray booth extending longitudinally along the path of thearticles to be painted having a configuration including an air exhaustelement with first and second surfaces sloping toward a bottom of thebooth and converging toward a slotted opening forming an exhaust inletextending longitudinally of the booth, and an adjustment mechanism foradjusting the width of the slot.

It is a feature of this invention that by adjusting the width of theexhaust element, a pressure drop is spread over the slot opening. Byadjusting the velocity of air flow through the exhaust elements in arange of 3,000 to 5,000 feet per minute, powder paint build-up at theexhaust inlet is substantially avoided.

It is a further feature of the present invention that the slanted inletwall configuration of the exhaust elements, in conjunction with theadjustment mechanism, improves uniformity of filter life by providing asubstantially even distribution of powder overspray at the filtermedia's location.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become apparentfrom a reading of a detailed description taken in conjunction with thedrawings, in which:

FIG. 1 is a perspective view of a paint spray booth utilizing a priorart booth air exhaust system;

FIG. 2 is a lateral sectional view of a paint spray booth incorporatingprior art longitudinal air exhaust elements:

FIG. 3 is a lateral sectional view of a paint spray booth with an airexhaust system arranged in accordance with the principles of the presentinvention;

FIG. 4 is an overhead view of an air exhaust element of the booth ofFIG. 3;

FIG. 5A is a lateral sectional view at one end of an air exhaust elementof the booth of FIG. 3;

FIG. 5B is a lateral sectional view at one end of an alternativeembodiment of an air exhaust element arranged in accordance with theprinciples of the present invention;

FIG. 6 is a partial sectioned side view of the air exhaust element ofFIG. 4; and

FIG. 7 is a partial sectional side view taken normal to a longitudinalaxis of a spray booth and showing an alternative arrangement of exhaustducts of the invention.

FIG. 8A is a lateral sectional view of an air exhaust element having abidirectional adjustment on the inlet slot according to the principlesof the present invention; and

FIG. 8B is a detail view of the bidirectional adjustment device shown inFIG. 8A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, a prior art paint powder spray booth 100includes laterally aligned exhaust boxes 110a-f positioned beneathgrated booth floor 108 to collect overspray from powder sprayapplicators such as 104a and 104b placed at various application stationslongitudinally along booth 100. As an article such as automobile body102 to be painted moves via a conveyor system 106 from an entrance end120 of a paint spray application zone 101 of booth 100 to an exit end122 of zone 101, paint is released from powder spray applicators 104aand 104b. Some of the paint from powder spray applicators 104a and 104bnever reaches the articles 102 to be painted and becomes overspray.Overspray from the powder spray applicators 104a,b passes through gratedfloor 108, located on either side of the conveyor system 106 andgravitates through an exhaust inlet 112 of one of the exhaust boxes110a-f which are laterally oriented just beneath the grated floor 108 oneither side of the conveyor system 106 and adjacent the bottom edges ofwall 118. The collected overspray in the exhaust boxes 110a-f is drawnthrough cartridge filters 114 and ducts 116 via exhaust fans 117 to apowder reclamation system (not shown) to prepare the exhausted overspraypowder for reuse.

Some of the exhaust boxes, such as 110a and 110b, are located generallybeneath the powder spray applicators 104a,b. These boxes 110a,b collectthe majority of overspray, while the remaining exhaust boxes 110c-f,nearer the entrance end 120 or the exit end 122 of the paint sprayapplication zone 101 collect relatively little overspray. Thedisproportionate amount of overspray collected in the exhaust boxes110a,b and filtered by cartridge filters 114 causes the cartridgefilters 114 in those boxes to wear out or become clogged in accordancewith their longitudinal positioning along the booth at different ratesrequiring replacement at non-uniform intervals.

With reference to FIG. 2, a prior art powder spray booth 200 includes apaint application zone 201 with longitudinally extending exhaustelements 202a and 202b positioned beneath spray applicators 214. A pairof service access floor gratings 224a and 224b are located on eitherside of a conveyor system 206. Beneath the gratings 224a,b and theexhaust elements 202a,b is a conventional grated floor 220 of booth 200.The paint separator system comprised of venturi passage 226,powder-laden water recovery chamber 228, dewatering baffle labyrinth 230and exhaust system 232, all located beneath grated floor 220 comprise aconventional arrangement which is isolated from (i.e., not in fluidcommunication with) longitudinally extending exhaust elements 202a and202b which are located just above the grated floor 220 on either side ofthe conveyor system 206 and adjacent the bottom edges of wall 218.Powder overspray exhaust elements 202a and 202b respectively includefirst sloping surfaces 208a, 208b and second sloping surfaces 210a,bconverging toward longitudinally extending slots 204a and 204b whichform exhaust inlets in each longitudinal exhaust element for thewithdrawal of spray-laden air therethrough.

Prior art booth 200 also includes a generally U-shaped or "horseshoe"shaped exhaust duct 216. In this prior art configuration, inwardlyflowing, longitudinally directed air is additionally exhausted from thespray application area via the U-shaped or horseshoe shaped exhaust duct216. The horseshoe shaped duct 216 withdraws the air from the booth andconveys it to a powder spray recovery area (not pictured) so that theoverspray may be later applied to an article 212 to be painted by powderspray applicators 214.

Horseshoe or U-shaped exhaust duct 216 could optionally be used in somecircumstances to supplement the air exhaust arrangement of the instantinvention to be described. Additionally, either a conventionalunderbooth separator/exhaust system as shown in FIG. 2 or remotecollectors can be used in conjunction with the present invention.

With reference to FIG. 3, paint spray booth 300 includes a tunnel-likepaint application zone 301 through which objects 312 are passed forpowder spraying by applicators 314. Exhaust elements 302a and 302b arelocated adjacent a conveyor system 306 along the path of an article 312to be painted. Overspray from powder spray applicators 314 gravitatestoward the bottom grated floor 303 of paint spray booth 300 where theoverspray encounters respective first sloping surfaces 308a and 308b andsecond sloping surfaces 310a and 310b of elements 302a and 302b. Eachpair of surfaces 308a, 310a and 308b, 310b converge respectively towardlongitudinally extending slots 304a and 304b which each form an exhaustinlet of respective exhaust elements 302a and 302b for the withdrawal ofspray-laden air therethrough. Adjusting mechanisms 312a and 312b enablethe width of inlets 304a and 304b, respectively, to be varied.Adjustments to the width 311 of exhaust inlet 304a and/or 304b enablecorresponding adjustment of air velocity through the inlet slotnecessary to obtain a desired pressure drop over the slot openings.Additionally, one could optionally, selectively control the amount ofdowndraft air flow in different booth sections along the longitudinalextension of the exhaust inlets 304a,b by varying slot widths 311. Forexample, a lower air flow may be desired between paint applicationstations in the booth, or longitudinal flow of ventilating air could bepromoted by lowering the exhaust air flow rates at the entrance and exitends of the booth.

With reference to FIG. 4, the exhaust element 302a includes the firstsloping surface 308a and the second sloping surface 310a convergingtoward the exhaust inlet 304a which extends substantially the entirelength from a first end 320 of the exhaust element 302a to a second end322 of the exhaust element 302a. The first and second sloping surfaces308a, 310a convey paint overspray through longitudinally extendingexhaust inlet 304a to yield powder of a uniform density for presentationvia a filtered exhaust system to a powder reclamation device (notshown).

With reference to FIG. 6, a side view of the exhaust element 302a ofFIGS. 3 and 4 is shown. The bottom-most point of the duct portion 328is, in side section, seen as a sloping line 324 generated by imparting alarger circumference to the duct portion 328 as one proceeds along itslongitudinal length (i.e. from left to right in FIG. 6). Hence the ductportion 328 has a surface sloping downwardly relative to a top edge 326of duct portion 328 of the exhaust element from first end 320 of element302a to second end 322. The sloping of duct portion 328, in conjunctionwith surfaces 308a and 310a and the longitudinally extending exhaustinlet 304a, provide an even distribution of powder in the air at outletduct 330 and a constant velocity of exhaust air along the length ofelement 302a - typically 3000 to 5000 feet per minute. Such uniformvelocity of powder overspray exiting the booth 300 via duct portion 328substantially reduces paint build-up at exhaust inlet 304a.

Outlet duct 330 directs exhausted powder overspray to a preferablyremotely located powder recovery system 332.

With reference to FIG. 5A, a first embodiment of a suitable exhaust slotwidth adjusting arrangement is shown. First and second sloping surfaces308a, 310a converge toward a longitudinally extending slot 304a whichforms the exhaust inlet of duct 328 for the withdrawal of spray-ladenair therethrough. The first sloping surface 308a is hingedly attached toa support plate 334 by a hinge element 338. The hinge element 338permits the slope of the first sloping surface 308a to be altered by athreaded element 336 which threadingly engages the support plate 334 andabuts at one of its ends first sloping surface 308a. The combination ofthe hinge element 338, the support plate 334, and the threaded element336 provide an adjustment mechanism for varying the slope of the firstsloping surface 308a, thereby adjusting the width 311 of thelongitudinally extending exhaust inlet 304a. The present inventioncontemplates that the second sloping surface 310a can also be equippedwith an adjustment mechanism to vary the width of the longitudinallyextending exhaust inlet 304a, alone or in combination with an adjustingmechanism associated with surface 308a, such as shown in FIG. 5A.

The angle 352 defined by the intersection of the first or second slopingsurfaces 308a. 310a with a line 350 extending perpendicularly to a planeof slot 304a has been found optimum if angle 352 is less than or equalto 45 degrees. Preferably this angle 352 lies in a range of 20 to 40degrees with a preferred value of 30 degrees.

With reference to FIG. 5B, an alternate embodiment of a longitudinalexhaust element 502 includes a first sloping surface 508, a secondsloping surface 510 and an exhaust duct 528 which are substantiallypliable to facilitate adjustment. A threaded element 536 threadinglyengages the first sloping surface 508 and second sloping surface 510 inopposite thread sense to provide an adjustment mechanism for adjustingthe width 511 of a longitudinally extending exhaust inlet 504. Sinceelement 536 is threaded in opposite senses in its engagement withsurfaces 508 and 510, surfaces 508 and 510 will be drawn toward or awayfrom each other as element 536 is rotated, thereby varying width 511.

It is understood that the adjusting apparatus of FIG. 5a or FIG. 5b isreplicated at preselected positions along the longitudinal extent of theexhaust elements 302a and 302b so as to effect width adjustments alongthe entire length of inlet slots 304a and 304b.

In its preferred embodiment, the present invention includes at least twoair exhaust elements, one on each side of the path of travel in thebooth of the articles to be painted. In the preferred arrangements aneven number of exhaust elements is used. More air exhaust elementspermit lower building height or space below the grated floor of thebooth. The number of air exhaust elements is limited by the width of thebooth, the preferred angles defined by the sloping surfaces convergingtoward the exhaust inlet, or both. An operator may configure the systemto create different flow rates or volumes in each longitudinal airexhaust element. Typically, the flow rate will be greater toward theouter walls of the booth than at the center thereof.

It is to be further understood that the invention contemplates virtuallyany arrangement for effecting adjustment of the exhaust slot width (e.g.311 of FIG. 5A or 511 of FIG. 5B) in addition to the two exampleembodiments set forth i n FIGS. 5A and 5B. For example, slidingpartitions extending along a plane of the slot opening or deformableduct material capable of retaining its deformed shape are consideredtechnically equivalent to the adjusting arrangements set forth herein.

An alternative exhaust system arranged in accordance with the principlesof the invention is set forth in FIG. 7, which is a longitudinal crosssection of the bottom portion of a zone 701 of a powder spray booth. Inany given zone, such as 701, exhaust elements could be arranged as shownin FIG. 7, such that pairs of exhaust elements 702 and 704, each havingrespective duct portions 706 and 708, with surfaces sloping from theends of zone 701 downwardly toward an outlet duct 710 positioned at apreselected location along the longitudinal extent of zone 701.

FIGS. 8A and 8B illustrate a further embodiment of a suitable exhaustslot with bidirectional adjusting arrangement. First and second slopingsurfaces 808, 810 converge toward a longitudinally extending slot 804which forms the exhaust inlet of duct 828 for the withdrawal ofspray-laden air therethrough. The exhaust slot with bidirectionaladjusting arrangement 806 is disposed below the first and second slopingsurfaces 808, 810 and bidirectionally varies the width 811 of theexhaust inlet 804 of the exhaust element 802.

With specific reference to FIG. 8B, the bidirectional exhaust slot withadjusting arrangement 806 is shown in greater detail. The first andsecond sloping surfaces 808 and 810 each connect with substantiallyvertical sidewalls 814a, 814b. Each of the substantially verticalsidewalls 814a, 814b are provided with a plurality of bolt holes 812a,812b. The bolt holes 812a, 812b receive bolts 836 which extend acrossthe exhaust inlet 804. A pair of angle brackets 850a, 850b are disposedadjacent to each of the bolt holes 812a, 812b, and the bolt 836 extendsthrough each of the angle brackets 850a, 850b. The angle brackets 850a,850b are provided with contact surfaces 852 and 854 which contact theouter surface of the exhaust inlet 804. A nut 844 is welded to one ofthe brackets 850b and the bolt 836 is rotated relative to the nut 844 inorder to draw the sidewalls 814 together or apart with respect to oneanother. The bolt 836 is also provided with a bolt collar 838 which isdisposed on an opposite side of the angle bracket 850a as compared tothe head 840 of the bolt 836.

In operation, rotation of the bolt 336 causes the sidewalls 814 of theexhaust inlet 804 to be symmetrically drawn toward or away from oneanother thereby providing a bidirectional adjustment for the exhaustinlet 804.

Finally, it will become apparent to those skilled in the art that theexample arrangements of the invention set forth in FIGS. 3 through 6readily lend themselves to modularization and retrofitting of existingconventional paint spray booths with traditional exhaust systems.

The invention has been described with reference to detailed descriptionsof preferred embodiments given for the sake of example only. The scopeand spirit of the invention are set forth in the appended claims.

We claim:
 1. In a paint spray booth having a longitudinally extendingpaint application zone through which articles to be painted are movedfrom an entrance end to an exit end thereof, at least one air exhaustelement extending longitudinally of the paint application zone, each ofsaid at least one air exhaust elements including first and secondsurfaces sloping toward a bottom of the paint application zone andconverging toward a slotted opening forming an exhaust inlet to anexhaust duct longitudinally extending along the paint application zone,the improvement comprising:adjusting means for varying a width of theexhaust inlet along a length of the exhaust duct; wherein a bottom-mostsurface of the exhaust duct slopes downwardly from one end of theexhaust element to a longitudinally opposite end of the exhaust element.2. The improvement of claim 1 wherein the adjusting means furthercomprises a fixed member hingedly coupled to one of the first and secondsurfaces and means coupled between the fixed member and the one of thefirst and second surfaces for imparting relative pivoted movementtherebetween.
 3. The improvement of claim 2 wherein the means forimparting relative pivoted movement comprises a threaded memberthreadingly engaging the fixed member.
 4. The improvement of claim 1wherein each exhaust element is flexible, and wherein the means foradjusting comprises means for moving the first and second surfacestowards and away from each other.
 5. The improvement of claim 4 whereinthe means for moving comprises a threaded element threadingly engagingat least one of the first and second surfaces.
 6. The improvement ofclaim 5 wherein the threaded element threadingly engages both the firstand second surfaces such that rotation of the threaded element in afirst rotational direction moves the first and second surfaces apartfrom each other and rotation of the threaded element in a secondrotational direction moves the first and second surfaces toward oneanother.
 7. The improvement of claim 4 further comprising the at leastone air exhaust element having a surface of the exhaust duct slopingdownwardly from one end of the exhaust element to an opposite end of theexhaust element.
 8. In a paint spray booth having a longitudinallyextending paint application zone having an entrance end and an exit end,a first exhaust element extending substantially longitudinally along abottom portion of the paint application zone from a vicinity of theentrance end toward the interior of the zone and a second air exhaustelement extending substantially longitudinally along a bottom portion ofthe zone from a vicinity of the exit end toward the interior of thezone, each of the first and second exhaust elements having alongitudinally extending slotted opening forming an exhaust inlet to alongitudinally extending exhaust duct and each of said first and secondexhaust ducts having a bottom-most surface sloping downwardlyrespectively from the entrance and exit ends of the paint applicationzone toward the interior of the paint application zone.
 9. The paintspray booth of claim 8 wherein each exhaust element includes adjustingmeans for varying a width the longitudinally extending slotted opening.10. The paint spray booth of claim 9 wherein the adjusting means furthercomprises a fixed member hingedly coupled to the exhaust duct adjacentthe slotted opening and means coupled between the fixed member and theexhaust duct for imparting relative pivoted movement therebetween. 11.The paint spray booth of claim 10 wherein the means for impartingrelative pivoted movement comprises a threaded member threadinglyengaging the exhaust duct.
 12. The paint spray booth of claim 9 whereineach exhaust element is flexible and wherein the means for varyingcomprise s means for moving opposite sides of the slotted openingtowards and away from each other.
 13. The paint spray booth of claim 12wherein the means for moving comprises a threaded element threadinglyengaging the exhaust duct.
 14. In a paint spray booth having alongitudinally extending paint application zone positioned above agrated floor of the booth through which articles to be painted are movedfrom an entrance end to an exit end thereof, at least one air exhaustelement extending longitudinally of the paint application zone andpositioned above the grated floor, each of said at least one air exhaustelements including first and second surfaces sloping toward a bottom ofthe paint application zone and converging toward first and secondgenerally parallel side walls forming an exhaust inlet to an exhaustduct longitudinally extending along the paint application zone, theimprovement comprising:bi-directional adjusting means for varying awidth of the exhaust inlet along a length of the exhaust duct, whereinthe bi-directional adjusting means includes a plurality of threadedelements which extend across a slotted opening of said exhaust inlet,each of said plurality of threaded elements extending through openingsin said first and second surfaces, wherein rotation of the threadedelement in a first rotational direction substantially symmetricallymoves the first and second surfaces apart from each other and rotationof the threaded elements in a second rotational direction substantiallysymmetrically moves the first and second surfaces toward one another.15. The improvement of claim 14 further comprising the at least one airexhaust element having a surface of the exhaust duct sloping downwardlyfrom one end of the exhaust element to an opposite end of the exhaustelement.